Process of purifying gases



March Z2,` 1932. F. H, sNYDgR E-r AL, 1,850,732

PROCESS OF'PURIFYING GASES Filed Feb. 21 1927 2 sheets-sheet 1 gru/vento@ FFfANcs HSNYDIJ( March 22, 12932. F. H, sNYDER ET Al. 1,850,732

l PROCESS OF PURIFYING GASES Filed Feb. 21. 1927 2 Sheets-Sheet 2 Patented Mam 22,t 1932 untreu STATES.

PATENT yorties v FRANCIS yH; kuNYl'llR `AND EDGAR D'. NEWKIRK, SYLR'JACUSE, NEW 'YYORIK PROCESS OF PURIFYINGGASES Application sled February 21, 1927.v seal No. 170,024.

' This invention relates to the purification kof gases and mixtures of gases and in its preferred embodiment relates particularly to the purification of impure hydrogen for inl5 dustrial uses. o

An 'important object of tbisinvention is to provide a simple, process for purifying impure gases and gaseous mixtures.

Another object of this invention is to pro vide a simple, economical and efficient process for purifying impure commercial hydrogen. A furtherfobject of this inventinon is to provide an -efhcient and economically prac- 5 tical process for purifying gaseous mixtures of'hydrogen and nitrogen, particularly for use in the production of nitrogen-bearing fertilizers and other commercial grades of ammonium salts."

A further object of this invention is to pro-- vide apparatus for eiciently carrying o, out the process above referred to.

' 'Other objects ,and advantages of this vinvention will be apparent from the following description.

In the accompanying drawings Wey have` shown in diagrammatic form the preferred construction of two modifications of appaY ratus suitable for carryingout our process. VIn this showing, s

Figure 1 illustrates a simplified form of apparatus for 'treating impure gases or mixtures of gases' containing` relatively small uble in aqueous ammonia, andv Y n Figure 2 illustrates a modied form of ap- 'p'aratus suitable for treating impure gasesy 'or mixtures of 'gasesy containing substantial o Y gas preheater 11 'which is 'of conventional construction and is providedy with a pair of headers 12 secured to the outer casing` of the preheater lland which are connected by tubes 'or pipes 13, which are,- adapted to conduct gases therethrough. YAny `suitable economical, and efficient amounts of impurities Which are readily soly means may be provided for heating the tubes 13 to raise the temperature of the gases passing therethrough but We prefer to employ a 'furnace 1sty arranged Vbelow vthe preheater 11 and adjacent the outlet end thereof and 4which vis adapted to discharge the products of `combustion therefrom into the preheater in contact With the tubes 13. The products of combustion from the. furnace 14 are vdirected in a circuitous path 'as indicated by the arrow shown in Figure 1 by means of staggered baffle plates 15 and are discharged from the lpreheatery 4through the, stack 16. After passingthrough the tubes or pipes 13 the gas or gases to be treated are discharged from the p'reheater 11 into the pipe 17 through Whichthey are conducted to the gas mixingchamber 18 of the hot gas purifier 19 Which is a catalytic converter of any suitable y conventional construction containing a cat-V 70 alyst yof the character hereinafter Vdescribed. f

which is capable of effecting the reaction of gases when they are introduced at a relatively low temperature into the/pipe 10. However, inthe eventthat the gas or gases to be treat'- ejd are at a suiicientlyelevated temperature when introduced into the pipe lOjthe preheater L11 is not Aemployed and the 'pipe 10 indicated as broken away'at the dotted line mm is extended and directly connected to theA pipe 17.at the point indicated bythe dottedy line Vyy in the drawings. o

The hot gaspurifi'er 19 is provided with a gas discharge pipe 2() which is connected to a heatl interchanger vv21. The heat interchanger 21 is of usual construction and comprises an outer casing, a pair of headers 22 secured to the outer casing, pipes or tubes 23,j connecting the headers in themanner of the` 95 usual tube boiler construction, and a baie plate` 2li-,arranged as indicated in the draw ings. The gases from the pipe20 are conducted through the .tubes 23 of the heat interchanger 21 A:and a pipe 25 into the gas scrub'-k ber 26. The scrubber 26 is provided with a f liquid inlet pipe 27, staggered bafile lates 28, a gas outlet pipe 29, and a liqui discharge pipe 30.

The outer casing of the heat interchanger 21 is provided with an ammonia gas inlet pipe 31 which conducts ammonia gas from any suitable source into the heat interchanger 21 wherein itis brought into contact with the exterior of the tubes 23 and is directed in a circuitous path as indicated by the arrow in the drawings by means .of the baille plate 24 and is discharged from the heat interchanger 21 into the pipe 32 which is connected to the gas mixing chamber 18 ofthe hot gas purifier 19.

Referrinor to Figure 2 of the drawings, the gas inlet pipe 10 is ordinarily connected to the pipe 33 but in the event that the gas or gases to be treated are not at the desired elevated temperature the connection between the pipe 10 and the pipe 33 is severed as at the olnt indicated by the dotted line w in the grawings and a preheater corresponding to the preheater 1l in Figure 1 is arranged between and in connection with the pipe 10 and the pipe 33. The gas or gases are conducted from the pipe 33 through the heat interchange'r 34, which is similar in construction to the heat interchanger 21 inFigure l of the drawings and discharged into the pipe and conducted therethrough to the pump l36. If desired for the purpose of regulating the temperature in the heat interchanger 34, a portion of the gases may be deflected by means of the damper 37 into the pipe 38 and by-passed around the heat interchanger 34 into theA pipe 35 as indicated in the drawings. The gas or gases are forced by means vof the pump 36 through the pipe 37 into the counter-current scrubber 40 which is provided with a liquid inlet pipe 41, a gas outlet pipe 42, a plurality of staggered baille plates 43 and a liquid discharge pipe 44. The ycooled gases discharged from the countercurrent scrubber 40 areconducted through the pipe 42 and the heat interchanger. 34 in a path indicated by the arrow in the drawings and are heated to the desired temperature before being discharged through the pipe 17 int-o ythe gas nixing chamber 18 of the hot gas purier 1 s Optionally, if the gases to be purified are cool, they may be led directly through the pipe 35 into the pump 36 by which they are forced through the scrubber 40 and discharged therefrom through the pipe 42. In this case a preheater similar to the preheater 11 yshown in Figure 1, is interposed between the pipe 42 and the pipe 17 in place of the heat interchanger 34.

It will be yreadily apparent upon reference to the drawings that the hot gas purifier 19, the heat interchanger 21, the scrubber 26, and

the connecting, inlet and outlet pipes shown through the pipe 46 and the pipe 30 to the inlet pipe 41. The washing liquid is drawn ofi' or purged from the apparatus by means of the discharge pipe 47 and the rate of discharge is controlled or regulated by means of the control valve 48. Ordinarily the amount of discharge from the pipe 47 is approximately equal to the amount of liquid' introduced into the scrubber 26 by means of the inlet pipe 27. 4

As heretofore set forth, our` process is particularly adapted for purifying impure commercial hydrogen or mixtures of hydrogen and nitrogen. According to the source of supply and manner of preparation such hydrogenk or gas mixture ordinarily contains substantial `amounts of carbon monoxid and carbon dioxid, varying small amounts of h drogen sulphid and other sulfur compounds, phosphorous compounds, arsenic compounds, and various otherimpurities present in small quantities. Most of these impurities are readily soluble in water or an aqueous ammoniacal solution and may be removed by bringing the hydrogen or gas mixture into intimate contact with such solvents. However, carbon monoxid and certain other impurities cannot be removed in this manner but we have discovered that these impurities can be converted into readily solublecompounds byl contacting them with ammonia gas at an elevated temperature in a manner hereinafter described.

In the preferred practice of our process impure commercial hydrogen or a mixture of hydrogen andy nitrogen is introduced into the apparatus by means of the supply pipe 10. As heretofore stated, if the hydrogen is not at a sufliciently elevatedv temperature it is introduced from the pipe 10 through the preheater 11. Thereafter, if necessary, the gases are subjected to a preliminary treatment in a manner hereinafter described to remove carbon dioxid and other impurities which are readily soluble in aqueous ammonia before they are introduced into the hot gas purifier 19. However, if the gases have been subjected to a preliminary treatment to remove these impurities or if such impurities are present' only in small amounts the gases are introduced at an elevated temperature into the mixing chamber 18 of the hot gas purifier 19. An excess of ammonia gas from any suitable source, f-such as an ammonia synthesis plant,

is introduced through the pipe 31 int-,ofthe heat -interchanger 21 Where the `temperature `of, such ammonia gas is elevated to the desired degree and the'ammonia is conducted through the pipei32 into ythe mixing chamber 18 Whereit is intimately mixed with the impure hydrogen introduced thereinto from the'pipe 1.7.. f

The primary function `of the hotfgas purifier 119 is vtovremove` thev carbon mono-xid `and certain Yother impurities from the impure gases by converting the impurities into readily removableV compounds such, for example, as forniamid Which is readily soluble inwater.

The hot gas purifier 19 is' maintained at a' temperature of from 0 to1,000? C., the optimum temperature being approxi-mately 350 C. Within this chamber the carbon monoxid and certain other impurities react lWith the gasespresent, particularly the ammonia gas introduced through pipe 32, to form soluble 4compounds"whichare later removed,` Under certain conditions the carbon monoxid reacts with the ammonia gas to form forniamid ac- `corfding to Vthe following equation:

00+NH3-4H00NH.

This'reactionis exothermic to the extent of 34,000 calories and is" quantitatively complete Within thetemperature range specified above.

`A calculation of the free energy equationfor vThus byk Nernsts 4formula logOO 17NH3 HO0NH2 Thus it Will be apparent that at the temperature specifiedL the reaction Will be practically complete audit will be obvious that such factors as an excess ofv VNH3 Will shift the equilibrium farther to the right in the equation given. In practice We have demonstrated that the reaction referred to is complete When dealing with gases containing any reasonably small `percentage of carbon monoxid. The foregoingy treatment of the mixture of gases to remove even substantial percentages of impurities present by means of gaseous ammonia at elevated temperatures +1.75 log T+S.

'has been found to be extremely satisfactory,

there being no detectable traces of such impurities left in the gas mixture after thisV treatment.

The reaction of carbon monoxid with ammonia in the purifier 19 can be conducted at a higher temperature, for example, at a temperature of fromk 500 to 700 C., in the presvora-gain employed inthefurth'er metals 'of the iron-'chromium group A'may be employed as catalysts. In #the presence of carbon` :monoxid We havepdisfcoveredthat l these catalysts 'have littl'eeffect 'upon the amrker:` 21 Where they serve to raise the temperature of` kthe :ammonia passing from the pipe 31 kthrough the heat interclianger to the purifier 19. F rom the lheat interchanger 21 the gases .are conducted through the pipe `25int0 --tlie scrubber k26 Where the soluble gaseous compounds formed in the purifier 19 are dissolved bythe Water introduced "through the pipe 27.` vvvhile Walter lis preferablyy employed as the gas scrubbing or Washing fluid in the scrubber'26y any suitable V.solveut'jof formamid and analogous compounds, such as an f aqueous -ammoniacialsolution, a weak acid solution and the like,may be employed in place of Water in the yscrubber 26. The

gases now completely purified except for minor quantitiesofwater vapor, are conducted-through the pipe 29 to storage tanks or gas holders 'or to otherapparatus.- The liquid from the scrubber 26 is discharged throughfthe pipe 30 `and 'collected if desired of gases. i

.As heretoforestated, if the gases ybeing treated containv 'substantial amounts of 'carbon dioxidand other impurities which are soluble in 'an aqueous a'mmoniacal solution,

the gases are first passed in the manner heretofore described through the counter-current scrubber 40 Where the solubleimpurities are removed and discharged through thepipe 47 before the gases are heated and introduced x.:

purification:

Vlioo duced through the inlet pipe 41 which passes f of the scrubber 40 which ispwithdrawn tliroughnthe pipe 44 and recirculated When and tothe extent desiredfby means of the pump 415 rthrough,.ftlie pipe 46v and the pipe 30 to the inlet pipe 41.

As set forth above 'anyk suitable Washing fluid is `employed in Athey scrubber 26 ybut Wa-z ter 'or an aqueous ammoniacal solution is preferably employed. The yaqueous .ammoniac'al solution from the' scrubber 26 is, :as

v downwardly Over'the baiiie plates Llfthrough 115 the scrubber 40. The ammoniacalf solution introduced into the JscrubberfiOy is supplied heretofore stated, preferably employed as the washing fluid in the scrubber 40 and as such Washing fluid passes downwardly through the scrubber 40 counter-currentwise to the current of the gases passing upwardly therethrough the soluble impurities are dissolved in the Washing fluid and removed from the gases. Since the amount of ammonia employed in the hot gas purifier 19 is substantially in excess of the amount required to react with the impurities present in the gases being treated the liquid discharged from the scrubber 26 and the scrubber 40 will contain in solution a substantial amount of ammonia and ammonia compounds in addition to other impurities removed from the gases being treated; and this liquid which is discharged through the pipe 30 or the pipe 47 may be collected and the compounds dissolved therein recovered and used without puriicaton for the producton of fertilizers or commercial grades of ammonium salts, such, for example, as ammonium sulfate or ammonium phosphate.

The partially purified gases are discharged from the scrubber 40 into the pipe 42 through which it is conducted into the heat interchanger 34 where its temperature is raised to the desired degree and are discharged into and conducted through the pipe 17 to themixin chamber 18 of the hot gas purifier 19 wherein the carbon monoxid and certain other impurities are converted into a readily soluble compound in the manner described.

`While the primary function of the hot gas purifier 19 is to convert the carbon monoxid present as an impurity in the gas under treatment into a readily'remo'vable compound or compounds various other impurities if present 1n small amounts are also converted into readily removable compounds by reaction with the gases present or formed in the hot gas purifier 19.

i I While we prefer to employ our process in connection with the purification of impure hydrogen it will be understood that such process together with the apparatus employedin connection therewith is adapted for the purification of other gases, such for example, as nitrogen and hydrogen-nitrogen mixtures to be employed in the synthetic production of ammonia. Moreover, while we have specified the contacting of the gas or gases to be treated with ammonia at an elevated temperature under certain favorable conditions depending upon the impurities present a certain measure of success can be obtained by contacting the gas or gases to be treated with ammonia in the gas purifier 19 at atmospheric temperatures.

Although we have illustrated the preferred form of apparatus it will be understood that they size, shape, and arrangement of parts may be changed to suit installation conditions and equivalent devices may be employed in place of those illustrated. For example, liquid spray tanks may be substituted for the scrubbers 26 and 40 and any suitable form of preheater may be substituted for the preeater 11; or a different design of heat interchanger substituted for the heat interchangers 2l and 34; or the temperature of the hot gas purifier 19 maybe maintained by the aplication of heat to or within the chamber ltself instead of heating the entering gases. From the foregoing it will be apparent that we have provided a simple, economical and eiicient process and apparatus for purifying impure gases or mixtures of gases and that our process and apparatus are particularly adapted for the purification of impure commercial hydrogen for industrial uses.

While we have described in detail the preferred vpractice of our invention ity is to be understood that the form of apparatus shown and described and the details of procedure may be varied without departing from the spirit of the invention or the scope of the sub- ]'oined claim.

We claim:

A process for removing impuritiesincluding carbon monoxide from hydrogen, nitrogen, or a mixture of hydrogen and nitrogen, which comprises contacting the gaseous material to be purified with ammonia gas at a temperature favorable to the reaction of the ammonia with impurities present to form water soluble reaction products, and contacting the resulting gaseous material with water to remove said Water soluble reaction products.

In testimony whereof we affix our signatures. FRANCIS H. SNYDER. EDGAR D. NEWKIRK. 

